The present invention relates to a diamond coated body with good adherence of the diamond layer and a high resistance to wear. In particular, the presently claimed invention relates to a cutting tool for cutting Al-alloys containing, e.g., Si and Cu as alloying elements and the like.
The production of thin layers of diamond directly from the gas phase by CVD or PVD technique is of great interest for the coating of cutting tools, drill bits, knives, etc. Gas phase deposition of diamond at useful deposition rates has been the subject for numerous researchers and a number of methods have evolved, all of which are plasma CVD methods.
The commercialization of diamond coated cutting tools has involved several years of research efforts, where the main problem has been achieving sufficient diamond layer adhesion onto the tool substrate material in a large-scale production method in order to make diamond coated cutting tools competitive from an economical point of view. At this stage, these problems have been generally solved and diamond coated cutting tools are produced and sold, see, I. Reineck, M. E. Sjostrand, J. Kamer, M. Pedrazzini, "HCDCA Diamond-Coated Cutting Tools", Diamond and Related Materials 5, 1996, pages 819-824. Having reached this level of development, further focus on production cost related issues is of vital importance.
The substrates of interest for diamond layers in cutting applications include cemented carbides and ceramics such as SiAlON and Si.sub.3 N.sub.4 and the deposition of diamond on these categories of substrates is well-known in the art. A standard method for achieving good diamond adhesion on cemented carbide substrates is to use diamond particles suspended in an ultrasonic bath wherein the tools substrates to be coated are treated prior to diamond deposition in order to scratch the tool surfaces to enhance the nucleation density. A high nucleation density is, however, not sufficient for achieving a good diamond layer adhesion--other parameters, such as control of the binder phase activity, in particular, that of cobalt, in a surface region is also important. Much work has been devoted to the enhancement of nucleation density for diamond growth, see, e.g., page 1173 of H. Liu and D. S. Dandy, "Studies on Nucleation Process in Diamond CVD: An Overview of Receipt Developments", Diamond and Related Materials 4, 1995, pages 1173-1188, for a review.
In B. Lux and R. Haubner, "Nucleation and Growth of Low-Pressing Diamond", Diamond and Diamond-like Films and Coatings, ed. R. E. Clausing et al., 1991, Plenum Press, New York, pages 579-609, polishing with Al.sub.2 O.sub.3 (1 .mu.m) is said not to enhance the nucleation density while this effect is obtained with diamond grits.
In U.S. Pat. No. 5,164,051, electrolytic polishing of cemented carbide, optionally combined with subsequent scratching with diamond, cBN, Al.sub.2 O.sub.3 or SiC is described. Diamond is the preferred scratching agent. The indication for good diamond layer adhesion is measured by means of a Rockwell indentation test where the layers are said to withstand a load of 5-25 kg without flaking.